Hi, im a new mac users. Usually in Windows, it will ask you for a password even if there is only one account on user setting. And there is an option to lock the computer (password will be asked if you want to unlock it). And i can't find such option in mac, i have only one user in user account, and i can only find an option to ask password when mac back from screen saver or sleep. Can i do a computer lock in mac? (if i want to leave my computer, and to be sure nobody plays with it, do i have to wait until the screen saver start..) And how to make the mac ask password when it's starting, can i do so? Thanks 